Update to 4.0.0-alpha.3 - Response Engines, 'inject' the context.JSON/JSONP/Text/Data/Markdown/Render, Read HISTORY.md

## 4.0.0-alpha.2 -> 4.0.0-alpha.3

**New**

A **Response Engine** gives you the freedom to create/change the
render/response writer for

- `context.JSON`
- `context.JSONP`
- `context.XML`
- `context.Text`
- `context.Markdown`
- `context.Data`
- `context.Render("my_custom_type",mystructOrData{},
iris.RenderOptions{"gzip":false,"charset":"UTF-8"})`
- `context.MarkdownString`
- `iris.ResponseString(...)`

**Fix**
- https://github.com/kataras/iris/issues/294

**Small changes**

- `iris.Config.Charset`, before alpha.3 was `iris.Config.Rest.Charset` &
`iris.Config.Render.Template.Charset`, but you can override it at
runtime by passinth a map `iris.RenderOptions` on the `context.Render`
call .
- `iris.Config.IsDevelopment` , before alpha.1 was
`iris.Config.Render.Template.IsDevelopment`

**Websockets changes**

No need to import the `github.com/kataras/iris/websocket` to use the
`Connection` iteral, the websocket moved inside `kataras/iris` , now all
exported variables' names have the prefix of `Websocket`, so the old
`websocket.Connection` is now `iris.WebsocketConnection`.

Generally, no other changes on the 'frontend API', for response engines
examples and how you can register your own to add more features on
existing response engines or replace them, look
[here](https://github.com/iris-contrib/response).

**BAD SIDE**: E-Book is still pointing on the v3 release, but will be
updated soon.

http.go

@@ -641,7 +641,7 @@ func joinMiddleware(middleware1 Middleware, middleware2 Middleware) Middleware {
 
 func profileMiddleware(debugPath string) Middleware {
 	htmlMiddleware := HandlerFunc(func(ctx *Context) {
-		ctx.SetContentType(contentHTML + "; charset=" + config.Charset)
+		ctx.SetContentType(contentHTML + "; charset=" + ctx.framework.Config.Charset)
 		ctx.Next()
 	})
 	indexHandler := ToHandlerFunc(pprof.Index)